Home Work Problem Set 7
7-1 The specific heat of a substance varies with temperature according to
c = 0.20 ＋ 0.14T ＋ 0.023T2, with T in °C and c in cal/g‧K. Find the energy
required to raise the temperature of 2.0 g of this substance from 5.0°C to 15°C.
(HRW18-38)
7-2 A gas within a closed chamber undergoes the cycle shown in the p-V diagram of
Fig. 18-37.The horizontal scale is set by Vs = 4.0 m3. Calculate the net energy added
to the system as heat during one complete cycle. (HRW18-43)
7-3 When a system is taken from state i to state f along path iaf in Fig. 18-42,
Q = 50 cal and W = 20 cal. Along path ibf, Q = 36 cal. (a) What is W along path ibf?
(b) If W = -13 cal for the return path fi, what is Q for this path? (c) If Eint,i = 10 cal,
what is Eint, f? If Eint,b = 22 cal, what is Q for (d) path ib and (e) path bf ? (HRW18-49)
FIG. 18-37 Problem 43
FIG. 18-42 Problem 49
FIG. 19-28 Problems 81
7-4 In the temperature range 310 K to 330 K, the pressure p of a certain nonideal gas
is related to volume V and temperature T by
How much work is done by the gas if its temperature is raised from 315 K to 325 K
while the pressure is held constant? (HRW19-12)
7-5 Figure 19-28 shows a hypothetical speed distribution for particles of a certain gas:
P(v) =Cv2 for 0<v≦v0 and P(v) =0 for v > v0. Find (a) an expression for C in terms of
v0, (b) the average speed of the particles, and (c) their rms speed. (HRW19-81)
7-6 Figure 19-27 shows a cycle undergone by 1.00 mol of an ideal monatomic gas.
The temperatures are T1 =300 K, T2 =600 K, and T3 =455 K. For 1 → 2, what are (a)
heat Q, (b) the change in internal energy ΔEint, and (c) the work done W?
For 2 → 3, what are (d) Q, (e) ΔEint, and (f) W? For 3 → 1, what are (g) Q, (h)
ΔEint, and (i) W? For the full cycle, what are (j) Q, (k) ΔEint, and (l) W? The initial
pressure at point 1 is 1.00 atm (=1.013 × 105 Pa). What are the (m) volume and (n)
pressure at point 2 and the (o) volume and (p) pressure at point 3? (HRW19-63)
7-7 (a) For 1.0 mol of a monatomic ideal gas taken through the cycle in Fig. 20-26,
where V1 = 4.00 V0, what is W/ p0V0 as the gas goes from state a to state c along path
abc? What is ΔEint/p0V0 in going (b) from b to c and (c) through one full cycle? What
is ΔS in going (d) from b to c and (e) through one full cycle? (HRW20-16)
7-8 Figure 20-29 shows a reversible cycle through which 1.00 mol of a monatomic ideal
gas is taken. Assume that p = 2 p0, V = 2 V0, p0 = 1.01 × 105 Pa, and V0 = 0.0225 m3.
Calculate (a) the work done during the cycle, (b) the energy added as heat during stroke
abc, and (c) the efficiency of the cycle. (d) What is the efficiency of a Carnot engine
operating between the highest and lowest temperatures that occur in the cycle? (e) Is
this greater than or less than the efficiency calculated in (c)? (HRW20-31)
FIG. 19-27 Problems 63
FIG. 20-26 Problems 16
FIG. 20-29 Problems 31